Look carefully. Something is happening in American politics. For the good. Democracy itself is striking back against the onslaught of anti-politics.

In Washington, Congress is doing its job and holding the zeal of an erratic president in check. Out in the country, states and cities are running policies of their own, on health care, climate change, gerrymandering, campaign finance and more.

We are seeing the volatility of the politics of anger. Anger is still involvement. Democracy would be worse off if the grass-roots were in apathy. Involvement can be turned from revenge to engagement.

In unrelated events but on the same day, October 19, George W. Bush and Barack Obama both stepped on to the political stage and spoke in defense of the values and principles of democracy.

Mr. Bush’s message, at a conference he himself convened, was stark. He spoke of fading confidence, a society torn apart by hatreds, the absence of common purpose, challenges to our most basic ideals, and the need to “recover our own identity.” Mr. Obama, for his part, had offered the same analysis in his final State of the Union Address, in January 2016. He called on his fellow Americans that “we fix our politics” to prevent “democracy from grinding to a halt.” A better politics, he said, “doesn’t mean we have to agree on everything, but it does require basic bonds of trust between its citizens. Democracy breaks down when the average person feels their voice doesn’t matter. Too many Americans feel that way right now.”

Much is at stake. Radical populism is sweeping America and Europe. The core democracies, the United States and the United Kingdom, are in crises of identity, following through to dysfunctional governance. Societies are torn asunder by extremes of inequality and animosity. Internationally, the People’s Republic of China is claiming the mantel of world leadership.

Leaders of authority in America and Europe are seeking to stimulate engagement from below to revitalize democracy. The George W. Bush Institute is launching a “call to action” to affirm democratic values and restore trust in democratic institutions. The recent Obama Foundation “summit” was a celebration of civic engagement trough examples of good practice. In Germany, President Frank-Walter Steinmeier is orchestrating a nation-wide deliberation for better understanding of the imperative of democracy. The concern is the same as expressed by Bush and Obama, to fortify the foundations of democratic culture.

The day Bush and Obama spoke for liberal democracy in America was also the second day of the Congress of the Chinese Communist Party in Beijing. Here, the leader Xi Jinping, who in his first five years has tightened all the screws of dictatorship, was celebrating, with audacious self-confidence, the superiority of autocracy over democracy.

In a comment (in the Süddeutsche Zeitung), the German author Kai Strittmatter called on the liberal democracies to “find their voice” up against the challenges of a threatening new world order under a totalitarian power state. Chinese autocracy promises prosperity on the condition that citizens give up their liberty. Liberal democracy promises both prosperity and liberty. Democracy has the moral high ground. But during his recent trip to Asia, the American president, the leader of the free world, had nothing to say about even basic human rights. The voice of democracy is not heard.

The politics of anger can go both ways, to more revenge or to more engagement. It is not unusual these days to find opinions in the press that democracy has had its day and is finished. But experienced leaders like Bush, Obama and Steinmeier are telling us that there is engagement out there waiting to be mobilized.

The time is right to turn from despondency to action. That requires a catalyst to tilt the balance. Democracy is ready to strike back, but that will not just happen, it must be taken in hand. As always, the democratic world needs American leadership. If America can “recover its identity” it can help the rest of us to “find our voice.”

Mr. Bush and Mr. Obama have committed themselves. Let us ask these two most recently retired Presidents, who, from each side of the political divide, see the same problem and understand the urgency of action in the same way, to join forces. Let us ask them to teach us that our divisions are not irreconcilable. Let us offer to join them with our engagement. Let us ask them to make themselves the catalyst of the democratic revival that is ready to happen. Let us ask them to merge their formidable authority to mobilizing groups and communities into a Campaign for Democracy. Let us ask the Campaign for Democracy to spread through the democratic world.